Heat 1 tablespoon of olive oil in a large skillet over medium-high heat until it shimmers. Season chicken breasts on both sides with salt and pepper, then place them in the hot skillet. Cook for 6 to 7 minutes per side until the internal temperature reaches 165 degrees Fahrenheit.

Remove the chicken to a clean cutting board and let it rest for 2 to 3 minutes. Using two forks, shred the chicken into bite-sized pieces. Set the shredded chicken aside on a plate.

In the same skillet, add the remaining 2 tablespoons of olive oil and heat over medium heat. Add the diced onion and bell peppers, stirring occasionally for about 5 minutes until they begin to soften.

Stir in the minced garlic and cook for 1 minute until fragrant. Add the Italian seasoning and red pepper flakes, stirring constantly for about 30 seconds.

Pour in the crushed tomatoes and chicken broth, stirring to combine. Bring the mixture to a simmer and let it cook uncovered for 8 to 10 minutes.

Reduce the heat to low and stir in the heavy cream until fully incorporated. Add the shredded chicken back to the skillet and stir gently to coat it in sauce. Taste and adjust salt, pepper, and red pepper flakes to your preference.

While the sauce simmers, bring a large pot of salted water to a rolling boil. Add the rigatoni and cook according to package directions until just al dente, usually 10 to 12 minutes.

Drain the cooked pasta in a colander and add it directly to the skillet with the chicken sauce. Gently fold everything together until the pasta is evenly coated.

Preheat oven to 375 degrees Fahrenheit. Transfer the pasta mixture to a 9x13 inch baking dish, spreading it into an even layer. Sprinkle the shredded mozzarella cheese evenly across the top, then scatter the crispy fried onions over it. Top with grated parmesan cheese.

Bake at 375 degrees Fahrenheit for 12 to 15 minutes until the cheese melts and begins to brown lightly. Serve immediately.